Land Mobile Radio Research Articles

Analysis of Land-Mobile Channel-Occupancy Sampling Errors

The results of an analysis of the errors made in sampling measurements of the Land-Mobile Radio Service channel occupancies by the mobile spectrum-occupancy monitors operated by the Federal Communications Commission are presented. Only the measurement errors caused by the limited observation interval (5 min out of a longer time period for each land-mobile channel) are considered in this paper. The major findings were: 1) That the normalized monitor occupancy-measurement error (obtained by dividing the monitor occupancy error by the respective channel occupancy) is larger for low-occupancy channels than for high-occupancy channels. 2) Monitor occupancy-measurement errors increase as the ratio of the 5-min observation time to the total measurement time decreases. 3) Larger relative occupancy-measurement errors occur in measuring 90-percent occupancy with the monitor than in measuring average occupancy. The 90-percent-occupancy value is defined as that value exceeded by only 10 percent of the samples. 4) A considerable percentage of both the 90-percent and average monitor sampling distributions tend to be normally distributed. 5) The distribution of 5-min occupancy samples taken consecutively on a LM channel for a period of a day (about 144 samples) usually is not similar to any common statistical distributions for low-occupancy channels. The. distribution of these samples on high-occupancy channels tends toward a normal distribution. 6) The distribution of 90-percent-occupancy samples taken by the monitor is usually asymmetric with respect to the 90-percent-occupancy value determined by use of all of the 5-min samples for a day.

Voice and data transmission in a mobile radio channel at 850 MHz

This paper is a review of those properties of a communications channel in the 850 MHz band that have importance to the quality of voice and data transmission for frequency modulated land mobile radio. The presentation is made with emphasis on the simpler aspects and consequences of the propagation environment encountered. The distribution of fading amplitude and rate and the distribution of fade durations are described such that a qualitative impression is gained of the effect of fades on voice transmission, and a quantitative description is obtained of their effect on data transmission.

Analysis of a partially-observed queuing system

This paper describes the behavior of communication on a land mobile radio channel and suggests a mathematical model to be used in analyzing such communication. Mobile radio is gaining wide recognition as an important business tool, but its growing use brings the problem of congestion. Although the communication on one radio channel by twelve different companies has the structure of a complex queuing system not all of which can be observed, the paper shows that such communication has some of the behavior of a simple queue. This facilitates the analysis of the radio channel and provides an illustration that models of simple queues may offer a helpful means of analyzing those which are more complicated. Once the situation can be analyzed it becomes possible to try to manage it as effectively as possible. In the case of mobile radio the analysis provides a means of measuring the cost of congestion under alternate circumstances.

Reducing Fuel Consumption With Land Mobile Radio

In a variety of situations the substitution of communication for transportation could be made, resulting in a reduction of fuel consumption. This paper examines the fuel savings that can be achieved when mobile radio communication is used to decrease the amount of driving by automobiles and trucks. Although this benefit is as varied as the operations which use radio, the general magnitude of the fuel savings is discussed. An indication of the way one might estimate the savings for a particular operation is provided. Reducing fuel consumption in this manner has a negative aspect which is briefly mentioned. Land mobile radio communication has become highly congested in recent years. Relief of the fuel consumption problem will increase radio congestion.

Spectral and Economic Efficiencies of Land Mobile Radio Systems

A variety of land mobile radio systems are compared by their spectral and economic efficiencies in providing various user services, system types covered are private one-channel, shared repeater one channel, controlled-access one-channel, trunked multichannel, and cellular. Spectral efficiency is defined to be the number of mobile users that can be served per MHz of spectrum in a core urban area, while economic efficiency is the average system cost per mobile. Both efficiencies vary with the type of usage, hence they are calculated for three major usages-mobile telephone service, dispatch emergency, and dispatch nonemergency. Services are described via seven service parameters, namely call holding time (average), tolerable average wait for channel access, peak busy hour utilization per mobile, audio quality (S/N), noise levels tolerable, and range. Sensitivity of the basic results to variations in the parameters are also computed and discussed.

Spectral and economic efficiencies of land mobile radio systems

A variety of land mobile radio systems are compared by their spectral and economic efficiencies in providing various user services. System types covered are private one-channel, shared repeater one channel, controlled-access one-channel, trunked multi-channel, and cellular. Spectral efficiency is defined to be the number of mobile users that can be served per MHz of spectrum in a core urban area, while economic efficiency is the average system cost per mobile. Both efficiencies vary with the type of usage, hence they are calculated for three major usages-mobile telephone service, dispatch service emergency, and dispatch service nonemergency. Services are described via seven "service parameters," namely call holding time (average), tolerable average wait for channel access, peak busy hour utilization per mobile, audio quality (S/N), noise levels tolerable, and service range. Sensitivity of the basic results to variations in the service parameters are also computed and discussed.

Spectrum conservation in the Land Mobile Radio Services

This article summarizes the ideas that are being actively discussed for use in mobile radio and, in particular, how they apply to the new 900-MHz region assigned to the Land Mobile Radio Services category. Over the next decade some of these methods will prove out and others will probably fall by the wayside. It is clear, however, that some new techniques will be necessary if mobile radio is to continue its growth.

Analysis of multiplex techniques for land mobile radio service

Two types of frequency multiplexing are theoretically analyzed for their applicability as a form of modulation in the land mobile radio service (LMRS). Both SSB/FM and FM/FM are analyzed for their signal-to-noise ratio (SNR) versus modulation index. These results are normalized to the signal-to-noise performances of the existing 5-kHz deviation system for comparison purposes. The latter performance is developed using the actual Electronic Industries Association (EIA) response of a LMRS receiver. The spectrum of the multiplex system for the case of equal subchannel signal-to-noise is developed using a computer. The spectrum is used to determine the spectrmm occupancy of multiplex systems. Based on the tradeoffs of transmit power and spectrum occupancy, a discussion of the interference characteristics of the multiplex systems compared to the existing system is presented. Finally, conclusions are drawn on the spectrum efficiency of a multiplex system compared to the present system.

Modulation methods and channel separation in the land mobile service

The following fundamental technical questions concerning the use of the spectrum allocated to the land mobile radio service are discussed. 1) Is it technically feasible to increase the number of assignable channels within the allocated spectrum space? 2) Are other modulation methods more or less suitable for providing more channels? The primary resource material used to answer these questions is the response of the Land Mobile Section, Industrial Electronic Division, Electronic Industries Association [49]. Only the frequency spacing question is treated in this paper.

Considerations of multiplexing techniques for the land mobile radio services [abstracts

Summary form only given. Frequency multiplexing techniques and theory with particular emphasis on its possible applicat,ions to the land mobile radio service are presented. Three forms of frequency multiplexing are analyzed: 1) frequency modulated subcarriers which are frequency modulated on a master carrier (FM/FM); 2) single sideband subcarriers which are frequency modulated on a carrier (FM/SSB); 3) single sideband subcarriers which are single sideband modulated on a carrier (SSB/SSB).

The land mobile radio services

Of the myriad uses of radio, probably the least known — and in many respects the least appreciated — are those encompassed under the general heading of the Land Mobile Services. These services involve, principally, two-way base-to-mobile and mobile-to-mobile voice communication systems. Every part of our industrial, social, and economic structure has found it possible to operate more efficiently and more effectively by adapting radio to its present-day needs. For the most part, these radio systems are now indispensable and are an integral part of the entities concerned, whether they be industrial, public-safety oriented, or any other type. But public knowledge of the extent of the organization of these activities around radio is extremely limited even though the public uses radio-equipped taxicabs and watches television enough to know that the police use two-way radio.

Low-Cost Pole-Mounted VHF Radio Station for Bonneville Power Administration

This paper describes what is believed to be the nation's first completely transistorized pole-mounted 10-watt VHF land mobile radio repeater station powered by a combination rechargeable battery and thermoelectric generator unit. Over 2 years of field experience has been accumulated since this Station was installed December 7, 1962. The Unique power supply, which has been an unqualified success, comprises a 12-watt thermoelectric generator, a thermomotor which diverts the waste heat into the radio equipment cabinet at temperatures below 40°F, and a nickel-cadmium battery supply.

The history of land-mobile radio communications

The history of land-mobile radio communications

The History of Land-Mobile Radio Communications

This paper on land-mobile radio communications was prepared for the noncommunications and nonmobile radio specialist. The early pioneering work of the police is covered, and after a brief statement about the early use of mobile transmitters, the Connecticut State Police two-way FM system is described. From the introduction of FM into the Connecticut system to the present, engineering efforts have been directed toward the improvement of selectivity, the elimination of spurious responses and spurious radiation of the equipment, and in general, toward technical improvements which would make possible both an increase in spectrum utilization and an increase in channel loading. In the more recent embodiments of equipments, transistors have been used for the power supply, for audio amplifiers, and for complete receiver circuit design. While the use of single-sideband modulation and the general characteristics of random-access systems are under investigation, advantages have not been disclosed which would justify a switch from FM to some other modulation system. The efficiency of frequency utilization must be increased, and any system which offers a substantial improvement over FM will be given careful attention.

System performance, compatibility, and standards

There are two prime purposes of Industry Standards for 2-Way Land Mobile Radio Equipment. They are: 1.) To assure high standards of customer performance and 2.) to assure system compatibility. Examples are given of standards written for both purposes. For example, the logic behind receiver sensitivity and selectivity standards are discussed. Similarily, the importance of standards which assure compatibility between Tone-Coded Squelch Systems, standards for frequency stability, and standards for interference protection between systems are discussed.